Biographical profile of the theoretical astrophysicist and aeronomist Alexander Dalgarno, centering on his professional life at the Center for Astrophysics. Early life and training in London. Schooling and entrance to University College, London. Recollections of wartime life in London and Aberdeen. College years and experiences as a student. Development of interest in mathematics. Friends, colleagues and teachers at college. Graduation in 1948 and contact with Harrie Massey which led him into physics. Research under Richard Buckingham on applications of quantum theory to problems in physics. Exposure to experimental physics and problems in geophysics. Contact with David Bates, Massey and Sydney Chapman. Move to Belfast to work with Bates on problems of aeronomy. Development of research themes at Belfast and conferences on upper atmospheric physics and how it changed from remote sensing to in situ observations. Continued discussion of the development of his research interests. Non-LTE studies. Summer at Massachusetts Institute of Technology (MIT), 1954 and contact with Air Force Cambridge Research Laboratory (AFCRL) upper atmosphere researchers. Appointment to Harvard-Smithsonian 1967. Students, postdocs and colleagues: Donald Menzel, Leo Goldberg. Refelections on relationship between Smithsonian Astrophysical Observatory (SAO) and Harvard College Observatory (HCO) in the late 1960s. United States Government Accountability Office (GAO) SAO audit, 1971 and the Greenstein Visiting Committee. Goldberg's resignation and Whipple's retirement from the SAO directorship. Restructuring the observatory. The issue of shared teaching loads between staffs of SAO and HCO. Dalgarno becomes acting director of the reorganized observatory, to be called the Center for Astrophysics, recollections of how and why he was chosen. His views on the controversy and the changing profile of astronomy at Harvard in the early 1970s. Searching for and naming the new director. Finding George Field and the creation of the Center for Astrophysics. Models considered for the new organization. Combining directorships and keeping the Chair of the department distinct. Relations with the National Science Foundation (NSF). Views on the reorganization and its divisions and assumption of the associate directorship of the theoretical astrophysics division. The Field years, 1970-1980. Festschrifts for Dalgarno.